Virus isolation studies were continued from the previous FY with samples taken from patients involved with the NIAID-AIDS treatment trials. Patient peripheral blood lymphocytes (PBL) were initially cocultured with normal PBL blasts. Virus was detected using the reverse transcriptase assay and the Dupont p24 antigen detection system. Attention was focused on adapting to tissue culture T cell lines, sequential isolates from 5 of these patients obtained over 4-year period. Work is currently in progress to analyze the variation in these isolates over tim as related to their antibody neutralization and DNA sequence patterns, in an attempt to correlate these changes with differences in clinical stages of AIDS. Similar studies focused on isolating and characterizing virus from PBL taken from AIDS patients in Chile. We found that many of the isolates as characterized by t polymerase chain reaction (PCR) and antibody neutralization crossreactivity were similar to the IIIB isolate while others were different. Further characterization will be necessary to see if they vary from other common isolates worldwide. A collaborative study was initiated with JHMC to do sequential virus isolations on PBL from AIDS patients before and after bone marrow transplantation. 5 patients have been followed to date with isolations performed on bone marrow and PBL every weeks. Results are variable, but generally have shown a virus reduction trend after transplantation. Follow-up virus isolation attempts on cocultivation of PBL and lymph nodes from rhesus monkeys immunized with HIV-1 in 1987 continue to be negative even after induction with 5-azacytidine. There have been no clinical changes in these animals, however 2 are still seropositive and all 4 show indications of harboring viral DNA when analyzed by the polymerase chain reaction technique.